Except Reddit has said that app developers aren't allowed to let users set their own API keys: https://www.reddit.com/r/Infinity_For_Reddit/comments/14c7v8...

Obviously for FOSS apps they can't stop someone from recompiling the app with their own API key baked in, but the barrier to entry there is significantly higher.

Why reddit is against users using their own api keys?

because they don't want the apps to stick around. that's why they're not negotiating, that's why they made the pricing so high (also to take advantage of AI scrapers), that's why they're making a bogeyman out of tpa devs.

Because this was never about getting a cut in 3rd party app revenue. They want to be the only app in town, one single experience that all ads can flow into.

Now it begs the question: why not force 3p apps to show ads to non-premium users? I imagine control is the answer there. Easier to show to adverts how good one app is doing then verifying proper ad placement in every 3p app.

Ahhh! Unsurprisingly, It seems like there is already a revanced patch for the Reddit sync app that allows you to use your own API key. So I guess users will just start doing it anyways, but still I wasn't aware of that restriction

The reddit API terms are written to imply not allowing users to bring their own key.

Given how antagonistic reddit has been to 3rd party apps during this one can assume they would make this explicit if anyone tried.

they already did make it explicit. https://www.reddit.com/r/Infinity_For_Reddit/comments/14c7v8...

it's 60rq/minute for free not per second https://github.com/reddit-archive/reddit/wiki/API